I've watched porn in mixed groups before and that was weeeeeeeird. Just a couple of times after coming back from bars downtown in Athens and this one girl and her boyfriend were always trying to get people to watch porn. Freaking weirdos.
Although, now that I think about it the internet really has changed the dynamics for watching porn. Since I'm old enough to remember the pre-internets porn era, there was a lot of "dude, check out my dad's smut mags" when you were teenagers and yes, even some "dude, I swiped a porn tape from my dad/older brother/uncle/pastor, come over and check it out!"